1. Field of the Invention
The present invention relates to a method and apparatus of color conversion from a red-green-blue (RGB) color space to a red-green-blue-white (RGBW) color space on an input image.
2. Description of the Prior Art
Currently, an LCD (Liquid Crystal Display) panel or an organic light emitting diode (OLED) display panel utilizes a red (R) sub-pixel unit, a green (G) sub-pixel unit, and a blue (B) sub-pixel unit to form one pixel unit. The LCD panel controls an R data of the red sub-pixel unit, a G data of the green sub-pixel unit, and a B data of the blue sub-pixel to mix a required color for displaying.
With the development of information technology, a variety of demands for the display panel are increased, such as high transmittance, low power consumption, and good image quality. The light transmittance and mixing efficiency of the current RGB color mixing method is relative low such that the power consumption is large and limits the improvement of the display panel. Accordingly, a display panel having four-color sub-pixel units formed by a red (R) sub-pixel unit, a green (G) sub-pixel units, a blue (B) sub-pixel unit and a fourth sub-pixel unit (for example, a white (W) sub-pixel unit) is designed in order to improve the display quality of the display panel based on three-color sub-pixel units.
In the prior art, and in a display panel having the four-color sub-pixel units, a minimum value of the RGB values is set as an output value of W (white) color. In this case, with the adding of the white sub-pixel unit, the brightness of the display panel having the four-color sub-pixel units is greatly increased, and the power consumption is also reduced. However, because the increase of the brightness, the display panel having the four-color sub-pixel units comparing with the display panel having three-color sub-pixel units is smaller in color gamut, and the color saturation is reduced, which results in worse local color performance. For example, the color saturation of a yellow object in an RGB input image having white background (i.e., high brightness and luminance) may be converted into khaki or yellow-green. Further, local detail performance may be damaged due to inappropriate white sub-pixel units.